The objective of this study was to define the role of radiotherapy alone for medically inoperable patients with Carcinoma in Situ (CIS) and Stage IA carcinoma of the uterine cervix. At the Mallinckrodt Institute of Radiology, Radiation Oncology Center from January 1959 through December 1986 21 patients with CIS and 34 with Stage IA were treated. All patients had histologically proven disease. The average age was 56 years for CIS and 51 years for Stage IA patients. Therapy for patients with CIS consisted of a single intracavitary insertion with a uterine tandem and colpostats. The average radiation doses were 4612 cGy to point A, 9541 cGy to the surface of the cervix, and 5123 milligram-hours (mgh). Radiotherapy for Stage IA tumors was delivered with intracavitary irradiation alone in 13 (average doses were 5571 cGy to point A, 10,430 cGy vaginal surface dose, and 6488 mgh). The other 21 patients were treated with external beam and intracavitary irradiation. The average whole pelvis dose was 1443 cGy with an additional 2354 cGy boost to the parametria with a midline stepwedge shield. The average intracavitary doses were 5200 cGy to point A, 10234 cGy to the vaginal surface, and 6293 mgh. None of the patients with CIS developed recurrent disease and none had severe sequelae of therapy. Only one patient with Stage IA developed recurrent disease in the pelvis. None developed metastatic disease. The severe complication rate was 5.9% (2/34) for Stage IA and only occurred in those receiving intracavitary irradiation and external beam irradiation. We conclude that irradiation consisting of intracavitary implants alone is excellent treatment for patients with medically inoperable Stage IA and CIS of the cervix.